Rescuers who worked overnight to rescue around 40 workers trapped after an under-construction tunnel on the Brahmakhal-Yamunotri National Highway collapsed here have established contact with them and provided them with food and water, officials said on Monday.

The workers are safe and have asked for food, which is being sent to them, the Silkyara police control room said, adding that communication has been established on walkie-talkies. Food packets have been supplied with the help of compressors, it said.

Dredging and drilling through the debris inside the under-construction tunnel between Silkyara and Dandalgaon is going on to prepare an escape passage for the trapped labourers, according to the district emergency operation centre.

A part of the tunnel collapsed on Sunday morning, leaving around 40 labourers trapped inside. The tunnel is part of the Char Dham all-weather road project.

According to the District Emergency Operation Centre, the labourers are from Bihar, Jharkhand, Uttar Pradesh, West Bengal, Odisha, Uttarakhand and Himachal Pradesh.

About 160 personnel of agencies such as the National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), Indo-Tibetan Border Police (ITBP) and the Border Roads Organisation (BRO) are trying to rescue the trapped labourers.

Officials on Sunday were optimistic about the safety of the trapped labourers as enough oxygen was made available to them through a water pipeline.

Prime Minister Narendra Modi spoke to Chief Minister Pushkar Singh Dhami on Sunday to enquire about the rescue efforts being carried out.

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